1. College of Geoscience and Surveying Engineering, China University of Mining & Technology (Beijing), Beijing 100083, China
2. Schobert International, LLC, Jordan, Minnesota 55352, United States
3. The EMS Energy Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
4. Kentucky Geological Survey, University of Kentucky, Lexington, Kentucky 40506, United States
5. Shanxi Research Institute of Coal Geological Survey, Taiyuan, Shanxi 030006, China